Diagnostic accuracy of thermal, hydration, and heart rate assessments in discriminating positive acute kidney injury risk following physical work in the heat.

Occupational heat stress increases the risk of acute kidney injury (AKI). This study presents a secondary analysis to generate novel hypotheses for future studies by investigating the diagnostic accuracy of thermal, hydration, and heart rate assessments in discriminating positive AKI risk following physical work in the heat in unacclimatized individuals. Unacclimatized participants (n = 13, 3 women, age: ∼23 years) completed four trials involving 2 h of exercise in a 39.7 ± 0.6 °C, 32 ± 3% relative humidity environment that differed by experimental manipulation of hyperthermia (i.e., cooling intervention) and dehydration (i.e., water drinking). Diagnostic accuracy was assessed via receiver operating characteristic curve analysis. Positive AKI risk was identified when the product of concentrations insulin-like growth factor binding protein 7 and tissue inhibitor of metalloproteinase-2 [IGFBP7∙TIMP-2] exceeded 0.3 (ng∙mL-1)2∙1000-1. Peak absolute core temperature had the acceptable discriminatory ability (AUC = 0.71, p = 0.009), but a relatively large variance (AUC 95% CI: 0.57-0.86). Mean body temperature, urine specific gravity, urine osmolality, peak heart rate, and the peak percent of both maximum heart rate and heart rate reserve had poor discrimination (AUC = 0.66-0.69, p ≤ 0.051). Mean skin temperature, percent change in body mass and plasma volume, and serum sodium and osmolality had no discrimination (p ≥ 0.072). A peak increase in mean skin temperature of >4.7 °C had a positive likelihood ratio of 11.0 which suggests clinical significance. These data suggest that the absolute value of peak core temperature and the increase in mean skin temperature may be valuable to pursue in future studies as a biomarker for AKI risk in unacclimatized workers.

Comparing Hypothermic and Thermal Neutral Conditions to Induce Metabolic Suppression.

Suppressing metabolism in astronauts could decrease CO2 production. It is unknown whether active cooling is required to suppress metabolism in sedated patients. We hypothesized that hypothermia would have an additive effect with dexmedetomidine on suppressing metabolism. This is a randomized crossover trial of healthy subjects receiving sedation with dexmedetomidine and exposure to a cold (20°C) or thermal neutral (31°C) environment for 3 hours. We measured heart rate, blood pressure, core temperature, resting oxygen consumption (VO2), resting carbon dioxide production (VCO2), and resting energy expenditure (REE) at baseline and each hour of exposure to either environment. We also evaluated components of the Defense Automated Neurobehavioral Assessment (DANA) Brief to evaluate the effect of metabolic suppression on cognition. Six subjects completed the study. Heart rate and core temperature were lower during the cold (56 bpm) condition than the thermal neutral condition (67 bpm). VO2, VCO2, and REE decreased between baseline and the 3-hour measurement in the cold condition (Δ = 0.9 mL/min, 56.94 mL/min, 487.9 Kcal/D, respectively). DANA simple response time increased between baseline and start of recovery in both conditions (20°C 136.9 cognitive efficiency [CE] and 31°C 87.83 CE). DANA procedural reaction time increased between baseline and start of recovery in the cold condition (220.6 CE) but not in the thermal neutral condition. DANA Go/No-Go time increased between baseline and start of recovery in both conditions (20°C 222.1 CE and 31°C 122.3 CE). Sedation and cold environments are required for metabolic suppression. Subjects experienced decrements in cognitive performance in both conditions. A significant recovery period may be required after metabolic suppression before completing mission critical tasks.

A psychobioecological model to understand the income-food insecurity-obesity relationship.

Food insecurity, defined by unpredictable access to food that may not meet a person's nutritional needs, is associated with higher BMI (kg/m2) and obesity. People with food insecurity often have less access to food, miss meals and go hungry, which can lead to psychological and metabolic changes that favor energy conservation and weight gain. We describe a conceptual model that includes psychological (food reinforcement and delay discounting) and physiological (thermic effect of food and substrate oxidation) factors to understand how resource scarcity associated with food insecurity evolves into the food insecurity-obesity paradox. We present both animal and human translational research to describe how behavioral and metabolic adaptations to resource scarcity based on behavioral ecology theory may occur for people with food insecurity. We conclude with ideas for interventions to prevent or modify the behaviors and underlying physiology that characterize the income-food insecurity-obesity relationship.

Partial and Complete Fluid Replacement Maintains Exercise Performance in a Warm Environment Following Prolonged Cold-Water Immersion.

ABSTRACT: Wheelock, CE, Stooks, J, Schwob, J, Hess, HW, Pryor, RR, and Hostler, D. Partial and complete fluid replacement maintains exercise performance in a warm environment following prolonged cold-water immersion. J Strength Cond Res 38(2): 290-296, 2024-Special warfare operators may be exposed to prolonged immersion before beginning a land-based mission. This immersion will result in substantial hypohydration because of diuresis. This study tested the hypothesis that both partial and full postimmersion rehydration would maintain performance during exercise in the heat. Seven men (23 ± 2 years; V̇o2max: 50.8 ± 5.3 ml·kg-1·min-1) completed a control trial (CON) without prior immersion and 3 immersion (18.0°C) trials without rehydration (NO) or with partial (HALF) or full (FULL) rehydration. After immersion, subjects completed a 60-minute weighted ruck march (20.4 kg; 5.6 kph) and a 15-minute intermittent exercise protocol (iEPT) in a warm environment (30.0°C and 50.0% relative humidity). The primary outcome was distance (km) covered during the iEPT. A priori statistical significance was set to p ≤ 0.05. Immersion resulted in 2.3 ± 0.4% loss of body mass in all immersion trials (p < 0.01). Distance covered during the first 13-minute interval run portion of iEPT was reduced in the NO rehydration trial (1.59 ± 0.18 km) compared with all other conditions (CON: 1.88 ± 0.18 km, p = 0.03; HALF: 1.80 ± 0.18 km, p < 0.01; FULL: 1.86 ± 0.28 km, p = 0.01). During the final 2 minutes of the iEPT, distance in the NO rehydration trial (0.31 ± 0.07 km) was reduced compared with the FULL rehydration trial (0.37 ± 0.07 km; p < 0.01) but not compared with CON (0.35 ± 0.07 km; p = 0.09) or HALF (0.35 ± 0.07 km; p = 0.08). Both partial and full postimmersion fluid replacement maintained intermittent exercise performance and should be applied as rehydration strategies.

Low back pain and biomechanical characteristics of back muscles in firefighters.

Firefighters often experience low back pain (LBP), but their back muscle characteristics are not well studied. This study aimed to 1) compare the biomechanical characteristics of back muscles and self-reported back disabilities in frontline firefighters with and without LBP history, and 2) examine the relationships between back disability and biomechanical measurements. We recruited 42 male firefighters and assessed their perceived pain and disabilities, maximum isometric back extension strength, passive stiffness, and fatigability of the longissimus. 54.8% of the participants experienced LBP within the past year. Those indicating higher pain intensity also had greater disability as indicated by the Oswestry Disability Index. There were no significant differences in strength, stiffness or fatigability of the back muscles between firefighters with and without LBP history. Multiple linear regression analysis revealed no significant relationship between the back disability and any biomechanical or demographic measures, likely due to the high functional abilities of the participants.

Approximately 50% of the firefighters who participated in the study experienced low back pain in the past 12 months. Since the pain level was mild to moderate, most of them continued to report to work. Biomechanically, there were no differences in back muscle strength, stiffness, resistance to fatigue, or left-right symmetry between firefighters with and without back pain history. Back disabilities were not related to any biomechanical measures or demographics including age and body mass index. Overall, despite experiencing some back pain, these frontline firefighters are highly functional and did not show diminished physical or neuromuscular responses.

Aerobic exercise performance is reduced following prolonged cold-water immersion.

Background: We tested the hypotheses that self-paced aerobic exercise performance is reduced following four hours of cold-water immersion when breathing air and further reduced when breathing 100% oxygen (O2). Nine healthy adults (four women; age 24 ± 3 years; body fat 17.9 ± 6.4%; VO2max 48±9 mL • kg • minute⁻¹) completed three visits: a no-immersion control trial and two experimental trials consisting of a four-hour cold-water immersion (20.1±0.3°C) either breathing air (FIO2 = 0.21) or O2 (FIO2 = 1.0). During the no-immersion control trial and following immersion in the experimental trials, subjects first completed a 60-minute ruck-march carrying 20% of body mass in a rucksack, immediately followed by an unweighted, self-paced 5-km time trial on a motorized treadmill. Core temperature, heart rate, and rating of perceived exertion were recorded every 1,000 meters during the 5-km time trial. Data are presented mean± SD. Time trial performance was reduced following immersion in both the 100% O2 trial (32±6 minutes; p=0.01) and air trial (32±5 minutes; p=0.01) compared to the control trial (28± 4 minutes). However, there was no difference between the 100% O2 and air trials (p=0.86). Heart rate, core temperature, and rating of perceived exertion increased during the time trial (time effect: p≺0.01), but were not different between trials (trial effect: p≥0.33). These findings suggest that prolonged cold-water immersion attenuates self-paced aerobic exercise performance, but does not appear to be further affected by breathing gas type.

Acute Effect of Night Shift Work on Endothelial Function with and without Naps: A Scoping Review.

We examined the breadth and depth of the current evidence investigating napping/sleeping during night shift work and its impact on non-invasive measures of endothelial function. We used a scoping review study design and searched five databases: Ovid Medline, EMBASE, Ovid APA PsycInfo, Web of Science Core Collection, and EBSCO CINAHL. We limited our search to English language and publications from January 1980 to September 2022. Our reporting adhered to the PRISMA-ScR guidance for scoping reviews. Our search strategy yielded 1949 records (titles and abstracts) after deduplication, of which 36 were retained for full-text review. Five articles were retained, describing three observational and two experimental research studies with a total sample of 110 individuals, which examined the non-invasive indicators of endothelial function in relation to the exposure to night shift work. While there is some evidence of an effect of night shift work on the non-invasive indicators of endothelial function, this evidence is incomplete, limited to a small samples of shift workers, and is mostly restricted to one measurement technique for assessing endothelial function with diverse protocols. In addition, there is no identifiable research investigating the potential benefits of napping during night shift work on non-invasive measures of endothelial function.

Carbohydrate or Electrolyte Rehydration Recovers Plasma Volume but Not Post-immersion Performance Compared to Water After Immersion Diuresis.

INTRODUCTION: We tested the hypothesis that a carbohydrate (CHO: 6.5%) or carbohydrate-electrolyte (CHO + E: 6.5% + 50 mmol/L NaCl) drink would better recover plasma volume (PV) and exercise performance compared to water (H2O) after immersion diuresis. METHODS: Twelve men (24 ± 2 years; 82.4 ± 15.5 kg; and V̇O2max: 49.8 ± 5.1 mL · kg-1 · min-1) completed four experimental visits: a no-immersion control (CON) and three 4-h cold-water (18.0 °C) immersion trials (H2O, CHO, and CHO + E) followed by exercise in a warm environment (30 °C, 50% relative humidity). The exercise was a 60-minute loaded march (20.4 kg; 55% VO2max) followed by a 10-minute intermittent running protocol. After immersion, subjects were rehydrated with 100% of body mass loss from immersion diuresis during the ruck march. PV is reported as a percent change after immersion, after the ruck march, and after the intermittent running protocol. The intermittent running protocol distance provided an index of exercise performance. Data are reported as mean ± SD. RESULTS: After immersion, body mass loss was 2.3 ± 0.7%, 2.3 ± 0.5%, and 2.3 ± 0.6% for H2O, CHO, and CHO + E. PV loss after immersion was 19.8 ± 8.5% in H2O, 18.2 ± 7.0% in CHO, and 13.9 ± 9.3% in CHO + E, which was reduced after the ruck march to 14.7 ± 4.7% (P = .13) in H2O, 8.8 ± 8.3% (P < .01) in CHO, and 4.4 ± 10.9% (P = .02) in CHO + E. The intermittent running protocol distance was 1.4 ± 0.1 km in CON, 1.4 ± 0.2 km in H2O, 1.4 ± 0.1 km in CHO, and 1.4 ± 0.2 km in CHO + E (P = .28). CONCLUSIONS: Although CHO and CHO + E better restored PV after immersion, post-immersion exercise performance was not augmented compared to H2O, highlighting that fluid replacement following immersion diuresis should focus on restoring volume lost rather than fluid constituents.

Diver Underwater Cycling Endurance After Short-Term Warm and Hot Water Acclimation.

INTRODUCTION: It is unclear whether immersion heat acclimation benefits exercise in warm water conditions. This study examined the effects of heat acclimation strategies on heart rate (HR), core temperature, and time to exhaustion (TTE) during cycling exercise in varying warm water conditions. METHODS: Twenty male divers completed this study at the Navy Experimental Diving Unit. Subjects were randomly assigned to one of two 9-day heat acclimation groups. The first group (WARM; n = 10) cycled for 2 hours at 50 W in 34.4 °C water, while the second group (HOT; n = 10) cycled for 1 hour against minimal resistance in 36.7 °C water. Following acclimation, TTE was tested by underwater cycling (30 W) in 35.8 °C, 37.2 °C, and 38.6 °C water. RESULTS: Throughout acclimation, the rate of core temperature rise in the first 30 minutes of exercise increased (P = .02), but the maximum core temperature reached was not different for either group. Time to exhaustion (TTE) was reduced, and the rate of core temperature rise during performance testing increased (both P < .001) with increasing water temperature but was not different between groups. Core temperature and HR increased throughout performance testing in each water condition and were lower in the HOT compared to the WARM acclimation group (all P < .05) with the exception of core temperature in the 37.2 °C condition. CONCLUSIONS: Underwater exercise performance did not differ between the two acclimation strategies. This study suggests that passive acclimation to a higher water temperature may improve thermoregulatory and cardiovascular responses to exercise in warm water. Hot water immersion adaptations are dependent on exercise intensity and water temperature.

Eating Patterns among Emergency Medical Service Providers in the United States: A Qualitative Interview Study.

Emergency medical service (EMS) providers experience demanding work conditions in addition to shift work, which increases risk for nutrition related chronic disease such as metabolic syndrome, diabetes, obesity, and cardiovascular disease. The high stress, emergent, and unpredictable nature of EMS may interfere with healthy eating patterns on and off shift, however little is known about how these conditions impact dietary patterns among EMS providers. This study aimed to understand factors impacting dietary patterns through semi-structured interviews with 40 EMS providers throughout the United States. Interviews were conducted virtually via Zoom video conference. Inductive coding was used to identify themes throughout the interviews. Salient factors mentioned in the interviews included hunger, fatigue, stress, coworker influence, ambulance posting, geographical location, agency policy, and culture. Factors were grouped into 4 domains: physiological factors, psychosocial factors, physical environment, and organizational environment, represented by an adapted version of the social ecological model of health behaviors to include factors influencing eating patterns specific to EMS, which may contribute to overall health. Various barriers to healthy eating exist within EMS, and future studies should explore interventions at each level of our proposed model to improve conditions and reduce nutrition related disease risk in this essential population.

Physical symptoms provoked by normobaric hot and humid disabled pressurized rescue module scenarios.

We tested the hypothesis that thermal discomfort will be greater, mood will be worse, and physical symptoms of heat illness will be exacerbated with elevations in dry bulb temperature during exposure to >95% relative humidity disabled pressurized rescue module simulation. On three occasions, 15 healthy males (23 ± 3 years) sat in 32.1 ± 0.1°C, 33.1 ± 0.2°C or 35.0 ± 0.1°C, and 95 ± 2% relative humidity normobaric environments for eight hours. Thermal discomfort (visual analog scale), mood (profile of mood states), and physical symptoms of heat illness, ear-nose-throat, and muscle discomfort (environmental symptoms questionnaire) were assessed before and following each hour of exposure. Thermal discomfort was greater throughout the exposure in 35°C versus both 32°C and 33°C (p ≥ 0.03) and did not differ between the latter conditions (p ≥ 0.07). Mood worsened over time in all trials (p ≺ 0.01) and was worse in 35°C compared to 32°C and 33°C after five hours of exposure (p ≤ 0.05). Heat illness symptoms increased over time in all trials and was greater in 35°C versus 32°C and 33°C throughout the exposure (p ≤ 0.04). Ear-nose-throat and muscle discomfort symptoms increased over time in all trials (p < 0.01) and were higher in 35°C versus 32°C and 33°C after the sixth hour of exposure (p ≤ 0.02). In support of our hypothesis, mood was worse, physical symptoms of heat illness, and ear-nose-throat and muscle discomfort symptoms were exacerbated, and thermal discomfort was greater with elevations in dry bulb temperature during an eight-hour exposure to a >95% relative humidity disabled PRM simulation.

Thermoregulation during a six-hour exposure to warm, humid hyperbaric conditions.

Purpose: In a disabled submarine scenario, a pressurized rescue module (PRM) may be deployed to rescue survivors. If the PRM were to become disabled, conditions could become hot and humid exposing the occupants to heat stress. We tested the hypothesis that the rise in core temperature and fluid loss from sweating would increase with rising dry bulb temperature. Methods: Twelve males (age 22 ± 3 years; height 179 ± 7 cm; mass 77.4 ± 8.3 kg) completed this study. On three occasions, subjects were exposed to high humidity and either 28-, 32-, or 35˚C for six hours in a dry hyperbaric chamber pressurized to 6.1 msw. Changes in core temperature (Tc) and body mass were recorded and linear regression lines fit to estimate the predicted rise in Tc and loss of fluid from sweating. Results: Heart rate was higher in the 35°C condition compared to the 28°C and 32°C conditions. Tc was higher in the 32°C condition compared to 28°C and higher in 35°C compared to the 28˚°C and 32°C conditions. Projected fluid loss in all of the tested conditions could exceed 6% of body mass after 24 hours of exposure endangering the health of sailors in a DISSUB or disabled PRM. A fluid intake of 1.0 to 3.5 L would be required to limit dehydration to 2% or 4% of initial mass depending upon condition. Conclusions: Prolonged exposure to 35°C conditions under pressure results in uncompensable heat stress. 32°C and 35°C exposures were compensable under these conditions but further research is required to elucidate the effect of increased ambient pressure on thermoregulation.

Rate of change in longitudinal EMG indicates time course of an individual's neuromuscular adaptation in resistance-based muscle training.

An individual's long-term neuromuscular adaptation can be measured through time-domain analyses of surface electromyograms (EMG) in regular resistance-based training. The perceived changes in recruitment, such as those measured during muscle fatigue, can subsequently prolong the recovery time in rehabilitation applications. Thus, by developing quantifiable methods for measuring neuromuscular adaptation, adjuvant treatments applied during neurorehabilitation can be improved to reduce recovery times and to increase patient quality of care. This study demonstrates a novel time-domain analysis of long-term changes in EMG captured neuromuscular activity that we aim to use to develop a quantified performance metric for muscle-based intervention training and optimization of an individual. We measure EMG of endurance and hypertrophy-based resistance exercises of healthy participants over 100 days to identify trends in long-term neuromuscular adaptation. Particularly, we show that the rate of EMG amplitude increase (motor recruitment) is dependent on the training modality of an individual. Particularly, EMG decreases over time with repetitive training - but the rate of decrease is different in hypertrophy, endurance, and control exercises. We found that the EMG peak contraction decreases across all subjects, on average, by 8.23 dB during hypertrophy exercise and 10.09 dB for endurance exercises over 100 days of training, while control participants showed negligible change. This represents approximately 2 dB difference EMG activity when comparing endurance and hypertrophy exercises, and >8 dB change when comparing to our control cases. As such, we show that the slope of the long-term EMG activity is related to the resistance-based exercise. We believe this can be used to identify person-specific performance metrics, and to create optimized interventions using a measured performance baseline of an individual.

Simultaneous assessment of motor and cognitive tasks reveals reductions in working memory performance following exercise in the heat.

This study tested the hypothesis that, following exercise in the heat, motor task performance will be impaired when assessed simultaneously with a cognitive task. In a randomized, crossover and counterbalanced design, twelve healthy adults (23 ± 2 years, 5 women) completed four 10-minute exercise circuits involving upper and lower body exercise in a moderate (18.1 ± 1.7°C, 38 ± 10% relative humidity) and a hot (40.3 ± 1.1°C, 26 ± 5% relative humidity) environment. Experimental testing was completed in a temperate thermal environment before exercise (~25°C) and in either the moderate or hot environment following exercise. The 3 Back test (a test of working memory) was used as the cognitive task and postural sway was used as the motor task. Cognitive and motor task performance assessments were conducted both individually (solo) and simultaneously (dual). At the end of exercise, core temperature (by 0.4 ± 0.3°C, P < 0.001), heart rate (by 12 ± 18 bpm, P = 0.025), and mean skin temperature (by 7.6 ± 0.8°C, P < 0.001) were higher in the Hot trial compared to Moderate. During solo testing, postural sway increased from pre- to post-exercise in the Hot (P ≤ 0.028), but not the Moderate (P ≥ 0.261) trial. During dual testing, postural sway did not differ between trials (P ≥ 0.065) or over time (P ≥ 0.094). During solo testing, 3 Back performance did not differ between trials (P = 0.810) or over time (P = 0.707), but during dual testing 3 Back performance following exercise was reduced in the Hot compared to the Moderate trial (P = 0.028). Simultaneous assessment of motor and cognitive tasks reveals that motor performance is reduced following exercise in the heat. .

Ad libitum drinking prevents dehydration during physical work in the heat when adhering to occupational heat stress recommendations.

Government entities issue recommendations that aim to maintain core temperature below 38.0°C and prevent dehydration [>2% body mass loss] in unacclimated workers exposed to heat. Hydration recommendations suggest drinking 237 mL of a cool sport drink every 15-20 min. This is based on the premise that ad libitum drinking results in dehydration due to inadequate fluid replacement, but this has never been examined in the background of recommendation compliant work in the heat. Therefore, we tested the hypothesis that ad libitum drinking results in >2% body mass loss during heat stress recommendation compliant work. Ten subjects completed four trials consisting of 4 hours of exposure to wet bulb globe temperatures (WBGT) of 24.1 ± 0.3°C (A), 26.6 ± 0.2°C (B), 28.5 ± 0.2°C (C), 29.3 ± 0.6°C (D). Subjects walked on a treadmill and work-rest ratios were prescribed as a function of WBGT [work:rest per hour - A: 60:0, B: 45:15, C: 30:30, D: 15:45] and were provided 237 mL of a cool sport drink every 15 min to drink ad libitum. Mean core temperature was higher in Trial A (37.8 ± 0.4°C; p = 0.03) and Trial B (37.6 ± 0.3°C; p = 0.01) versus Trial D (37.3 ± 0.3°C) but did not differ between the other trials (p ≥ 0.20). Body mass loss (A: -0.9 ± 0.7%, B: -0.7 ± 0.5%, C: -0.3 ± 0.5%, D: -0.4 ± 0.6%) was greater in Trial A compared to Trial D (p = 0.04) and was different from 2% body mass loss in all trials (p ≤ 0.01). Ad libitum drinking during recommendation compliant work in the heat rarely resulted in dehydration. Registered Clinical Trial (NCT04767347).

Do the National Institute for Occupational Safety and Health recommendations for working in the heat prevent excessive hyperthermia and body mass loss in unacclimatized males?

The National Institute for Occupational Safety and Health recommendations for work in the heat suggest workers consume 237 mL of water every 15-20 min and allow for continuous work at heavy intensities in hot environments up to 34 °C and 30% relative humidity. The goal was to determine whether the National Institute for Occupational Safety and Health recommendations prevented core temperature from exceeding 38.0 °C and greater than 2% body mass loss during heavy-intensity work in the heat. Eight males consumed 237 mL of water every 20 min during 2 hr of continuous heavy-intensity walking (6.4 kph, 1% grade) in a 34 °C/30% relative humidity environment, in accordance with the National Institute for Occupational Safety and Health recommendations. Projected core temperature and percent body mass loss were calculated for 4 and 8 hr of continuous work. Core temperature rose from baseline (36.8 ± 0.3 °C) to completion of 2 hr of work (38.1 ± 0.6 °C, p < 0.01), with two participants reaching the 38.0 °C threshold. Projected core temperatures remained elevated from baseline (p < 0.01), did not change from 2 to 4 hr (38.1 ± 0.7 °C, p > 0.99) and 4 to 8 hr (38.1 ± 0.8 °C, p > 0.99), respectively, and one participant exceeded 38.0 °C at 4 to 8 hr. There was no change in body mass loss over time (p > 0.99). During 2 hr of continuous heavy-intensity work in the heat, 75% of participants did not reach 38 °C core temperature and 88% did not reach 2% body mass loss when working to National Institute for Occupational Safety and Health recommendations.

Functional versus conventional strength and conditioning programs for back injury prevention in emergency responders.

Back pain and back-related injuries are common complaints among emergency responders. The purpose of this study was to compare the effectiveness of two strength and conditioning programs in improving back muscle characteristics and disabilities in emergency responders (firefighters/paramedics). Participants (n = 24) were randomized into two groups to complete 16 weeks of supervised exercise intervention: 1) Functional training used unilateral movements that mimicked the asymmetrical nature of emergency operations, 2) Conventional training performed bilaterally loaded exercises. Outcome measures were maximum isometric back extension strength, passive muscle stiffness, lumbar extensor fatigability, and revised Oswestry Low Back Pain Questionnaire. A mixed model Analysis of Variance with repeated measures was performed to compare the difference over time and between groups. While the training effects were similar between groups, both programs improved isometric back extension strength (+21.3% functional, +20.3% conventional, p < 0.001, ηp 2 = 0.625) and lumbar extensor muscle fatigability (+17.4% functional, +9.5% conventional, p = 0.009, ηp 2 = 0.191). Bilateral symmetry in muscle stiffness was improved as indicated by reduction in symmetry index (-7.1% functional, -11.8% conventional, p = 0.027, ηp 2 = 0.151). All self-reported pain and disability scores fell within the category of "minimum functional limitation" throughout the intervention and 6-month follow-up periods. For frontline firefighters and paramedics, both functional and conventional strength training are effective for improving back muscle characteristics.

Effects of hyperbaric oxygen therapy on exercise-induced muscle damage.

Purpose: To perform a literature review on hyperbaric oxygen (HBO2) therapy as a treatment for exercise-induced muscle damage (EIMD). Methods: PubMed, Web of Science and Google Scholar were searched for articles related to HBO2 therapy as a treatment for exercise-induced muscle damage. Inclusion criteria included HBO2 therapy as the primary intervention to treat EIMD. Articles used in this review ranged from 1995-2021. Conclusion: Current literature on the effectiveness of HBO2 therapy to treat EIMD is mixed. Early and frequent treatments seem to be important factors when it comes to the success of HBO2 therapy. Additional research is needed to determine if HBO2 therapy has potential to treat more severe forms of EIMD and the role HBO2 therapy has on inflammation and satellite cell function after EIMD.

Physical Exertion Partially Mitigates Task-Switching Deficits From Sleep Loss: Implications for Firefighters.

OBJECTIVE: The aim of the study is to investigate effects of physical exertion on cognitive deficits from sleep loss under conditions that mimic a firefighting scenario. METHODS: Twenty-four male participants completed a crossover study design with 3 conditions: total sleep deprivation, sleep disruption (three 60-minute awakenings), and rested control. Participants then completed 50 minutes of a physical exertion task involving treadmill exercise in a heated room while wearing firefighter protective clothing. Vigilant attention and task-switching performance were assessed pre- and post-sleep manipulation and pre- and post-physical exertion. Vigilant attention was also assessed mid-physical exertion. RESULTS: Total sleep deprivation and sleep disruption increased attentional lapses and task-switching RT. Total sleep deprivation additionally reduced task-switching accuracy. Performance after physical exertion improved only for task-switching RT after total sleep deprivation. CONCLUSIONS: Physical exertion selectively mitigated task-switching RT deficits from the most severe sleep loss condition, total sleep deprivation.